Testing/Diagnosing Bed Heater ?

Hi All

Sorry if this is a really stupid and basic question But !!!

I have a Duet 0.8.5 board and a seriously do not want to blow it up.

I have a degree in mechanical engineering and never before has a piece of electronics made me feel so bloody stupid !!! intuitive it's not.

I am just commissioning my P3Steel and working through getting it up and running, I have just completed end stop tests and auto bed compensation successfully.

I have This Heat-bed wired through This 12v 30amp PSU heatbed meters out around 2.2 ohms

The 12v positive power line in to the board is fuse protected.

Running 1.13b DC42 firmware.

How do I physically turn the bed on in the web interface to test it ?

Here is my take on it !!

Upon opening the web interface, then looking at the top left corner entitled "Heater Temperatures" in that section I have 4 columns

(Blank) --------------------------- Current ---------------------------------- Active ---------------------------- Standby--------------------

Heater 1: active (T0) ---------- 34.2c ------------------------ 0 c(with drop down tab) ------------ 0 c(with drop down tab)

Bed: active ----------------------- 33.9c------------------------- 0 c(with drop down tab) ------------------ (Blank)

I surmise that you just go to the "Active" tab and choose from the list of temps to test it turns of and observe to see if the "current" temps scale rises to the chosen temperature ?

Or am I missing something else completely !!!

Quote
Calvinx66
I surmise that you just go to the "Active" tab and choose from the list of temps to test it turns of and observe to see if the "current" temps scale rises to the chosen temperature ?

Yes, or you can type a temperature into the Active box.

2.2 ohms is a very high resistance for a 12V bed heater. It should be about half that. Have you connected one of the bed heater wires to both pins 2 and 3 for 12V operation, as the table on the heater says?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for the reply and confirmation, I thought I was going mad!!!

Yes soldered to both pins for 12v operation. This bed was operating fine in this configuration on a RAMPS controller though.

I will remove it and test at the PCB again though.

Thanks

As an update

I have checked the Heat Bed and all visually checks out, but still reads 2.2 ohms @ 12v, so I have an new bed on order !!

Quote
Calvinx66
As an update

I have checked the Heat Bed and all visually checks out, but still reads 2.2 ohms @ 12v, so I have an new bed on order !!

It sounds to me that one of the two circuits on the heat bed may have gone open circuit. If you disconnect the wire going to pins 2 and 3, you should be able to measure about 2.4 ohms between pins 1 and 2, and 2.4 ohms between pins 1 and 3. So about 1.2 ohms when you connect them both in parallel.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].